/usr/share/upstart/sessions/untrusted-helper-type-end.conf is in ubuntu-app-launch 0.5+15.10.20150817-0ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | description "End all untrusted helpers of a particular type, usually when the manager ends"
start on untrusted-helper-type-end
instance ${HELPER_TYPE}
emits untrusted-helper-end
exec /usr/lib/x86_64-linux-gnu/ubuntu-app-launch/untrusted-helper-type-end
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